Apparatus and method for controlling operation of compressor

ABSTRACT

An apparatus for controlling an operation of a compressor includes a controller for generating a control signal for selecting an operation mode of a compressor according to an operation load of the compressor; a first switching unit connected to a motor including a main coil and a sub-coil, and selecting only the main coil or both the main coil and the sub-coil according to the control signal; first and second capacitors electrically connected to the first switching unit; and a second switching unit connected to the first capacitor and selectively connecting the first capacitor in parallel to the second capacitor according to the control signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a compressor and, more particularly, to an apparatus and method for controlling an operation of a reciprocating compressor.

2. Description of the Prior Art

In general, a reciprocating compressor does not employ a crank shaft for converting a rotational motion to a linear motion, so it has higher compression efficiency than a general compressor.

When the reciprocating compressor is used for a refrigerator or an air-conditioner, a compression ratio of the reciprocating compressor can be varied by varying a stroke voltage inputted to the reciprocating compressor in order to control cooling capacity.

A conventional reciprocating compressor will now be described with reference to FIG. 1.

FIG. 1 is a block diagram showing the construction of an apparatus for controlling an operation of a reciprocating compressor in accordance with a conventional art.

As shown in FIG. 1, the conventional apparatus for controlling an operation of the reciprocating compressor includes: a voltage detector 14 for detecting a voltage applied to a reciprocating compressor 13 as a stroke of the reciprocating compressor 13 is varied; a current detector 12 for detecting a current applied to the reciprocating compressor 13 as the stroke of the reciprocating compressor 13 is varied; a microcomputer 15 for calculating a stroke based on the voltage value detected by the voltage detector 14 and the current value detected by the current detector 12, comparing the calculated stroke with a stroke reference value, and generating a switching control signal according to the comparison result; and a power supply unit 11 for supplying a stroke voltage to the reciprocating compressor 13 by controlling ON/OFF of AC power supplied to the reciprocating compressor 13 with an internal triac (Tr1) according to the switching control signal generated by the microcomputer 15.

The reciprocating compressor 13 receives a stroke voltage provided to an internal motor (not shown) according to the stroke reference value set by a user, varies the stroke, and reciprocally moves an internal piston (not shown).

The operation of the conventional apparatus for controlling an operation of the reciprocating compressor will now be described.

First, when a voltage is supplied to the internal motor according to the user's set stroke reference value, the reciprocating compressor 13 varies the stroke and reciprocally moves the piston. Herein, the stroke means a distance along which the piston of the reciprocating compressor 13 is reciprocally moved.

The turn-on duration of the triac (Tr1) of the power supply unit 11 is lengthened by the switching control signal outputted from the microcomputer 15, and accordingly, the AC power is supplied to the reciprocating compressor 13 to drive the reciprocating compressor 13. At this time, the voltage detector 14 and the current detector 12 detect the voltage and the current applied to the reciprocating compressor 13, respectively, and output the detected voltage and current values to the microcomputer 15.

The microcomputer 15 calculates the stroke of the reciprocating compressor 13 base don the voltage and current values respectively detected by the voltage detector 14 and the current detector 12, compares the calculated stroke value with the stroke reference value, and generates a switching control signal according to the comparison result. For example, if the calculated stroke value is smaller than the stroke reference value, the microcomputer 15 outputs a switching control signal for lengthening the turn-on duration of the triac (Tr1) to the power supply unit 11 to increase the stroke voltage supplied to the reciprocating compressor 13.

If, however, the calculated stroke value is greater than the stroke reference value, the microcomputer 15 outputs a switching control signal for shortening the turn-on duration of the triac Tr1 to the power supply unit 11 to reduce the stroke voltage supplied to the reciprocating compressor 13.

The single capacitor 16 connected in series to the internal motor of the reciprocating compressor 13 countervails an inductance of a coil wound in the internal motor.

Meanwhile, in the conventional apparatus for controlling an operation of the reciprocating compressor, when the voltage is applied to the motor of the compressor 13 through the triac Tr1 in order to control the stroke of the compressor, a noise is generated. In order to cancel the noise, a relay 17 and a motor 18 consisting of a main coil 19 and a sub-coil 20 as shown in FIG. 2 are required.

For example, the relay selects only the main coil 19 or both the main coil 19 and the sub-coil 20 according to a change in the voltage inputted to the compressor and a change in an operation load of the compressor, to thereby vary capacity of the motor 18. For example, if an inputted voltage is increases or an operation load of the compressor is greater than a pre-set reference load (namely, in case of an overload), the microcomputer 15 controls the relay 17 to select only the main coil 19 to reduce a back electromotive force constant of the motor 18.

Meanwhile, if the voltage inputted to the compressor is reduced or the operation load of the compressor is smaller than the pre-set reference load (namely, underload), the microcomputer 15 controls the relay 17 to select both the main coil 19 and the sub-coil 20 to increase the back electromotive force constant of the motor 18. Herein, the operation mode of the compressor is changed to a power mode or a safe mode according to the change in the voltage inputted to the compressor and the change in the operation load of the compressor. The power mode refers to a method in which the motor is operated through only the main coil while the safe mode refers to a mode in which the motor is operated through both the main coil and the sub-coil.

The number (N) of times of winding of the coil wound at the motor 18 of the reciprocating compressor is proportional to the back electromotive force constant of the motor, so when a certain voltage is applied to the compressor, the stroke of the compressor and the number of times of winding of the coil are in inverse proportion as expressed in equation (1) shown below: $\begin{matrix} {{Stroke} \cong \frac{Voltage}{MotorConstant} \propto \frac{Voltage}{N}} & (1) \end{matrix}$

Accordingly, the motor can be controlled by varying its capacity by controlling the relay 17 according to the change in power applied to the compressor and the change in the operation load of the compressor.

However, as for the apparatus for controlling an operation of the reciprocating compressor in accordance with the conventional art, when the compressor is in the power mode or in the safe mode, power is applied to the motor 18 of the compressor through only one capacitor connected to the motor 18, causing a problem that the operation of the compressor is unstable. For example, when the operation mode of the compressor is changed from the safe mode to the power mode or from the safe mode to the power mode, the number of times of winding of the coil of the motor is changed and thus the inductance of the motor coil is changed. But since the compressor is operated through only one capacitor, the compressor is operated unstably.

U.S. Pat. No. 6,644,943 issued on Nov. 11, 2003 also discloses a reciprocating compressor.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide an apparatus and method for controlling an operation of a compressor capable of operating stably a compressor by varying capacitance of a capacitor electrically connected to a motor of the compressor when a value of inductance of a motor coil is changed according to an operation load of the compressor.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an apparatus for controlling an operation of a compressor including: a controller for generating a control signal for selecting an operation mode of a compressor according to an operation load of the compressor; a first switching unit connected to a motor including a main coil and a sub-coil, and selecting only the main coil or both the main coil and the sub-coil according to the control signal; first and second capacitors electrically connected to the first switching unit; and a second switching unit connected to the first capacitor and selectively connecting the first capacitor in parallel to the second capacitor according to the control signal.

To achieve the above object, there is also provided an apparatus for controlling an operation of a reciprocating compressor including: a voltage detector for detecting a voltage applied to a reciprocating compressor as a stroke of the reciprocating compressor is varied; a current detector for detecting a current applied to the reciprocating compressor as the stroke is varied; a microcomputer for calculating a stroke based on the voltage value detected by the voltage detector and a current value detected by the current detector, comparing the calculated stroke with a stroke reference value, generating a switching control signal according to the comparison result, and generating a mode control signal for selecting an operation mode of the reciprocating compressor according to an operation load of the reciprocating compressor; a power supply unit for supplying a stroke voltage to the reciprocating compressor by ON/OFF controlling AC power applied to the reciprocating compressor with an internal triac; a first switching unit connected to a motor including a main coil and a sub-coil installed in the reciprocating compressor, and selecting only the main coil or both the main coil and the sub-coil according to the mode control signal; first and second capacitors electrically connected to the first switching unit; and a second switching unit connected to the first capacitor and selectively connecting the first capacitor in parallel to the second capacitor according to the mode control signal.

To achieve the above object, there is also provided a method for controlling an operation of a compressor including: a step in which if an operation load of a compressor is greater than a reference load, power is applied to a main coil of a motor of the compressor, and at the same time, first and second capacitors connected to the motor are connected in parallel; and a step in which if the operation load of the compressor is smaller than the reference load, power is applied to the main coil and the sub-coil of the motor of the compressor, and at the same time, one of the first and second capacitors connected to the motor is opened.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a block diagram showing the construction of an apparatus for controlling an operation of a compressor in accordance with the conventional art;

FIG. 2 is a block diagram showing the apparatus for controlling an operation of the compressor including a motor consisting of a main coil and a sub-coil in accordance with the conventional art;

FIG. 3 is a block diagram showing an apparatus for controlling an operation of a compressor in accordance with the present invention;

FIG. 4 is a flow chart of a method for controlling an operation of a compressor in accordance with the present invention;

FIG. 5 is a block diagram showing an operation of the apparatus of controlling an operation of the compressor when an operation mode of the compressor is changed to a power mode in accordance with the present invention; and

FIG. 6 is a block diagram showing an operation of the apparatus for controlling an operation of the compressor when the operation mode of the compressor is changed to a safe mode in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An apparatus and method for controlling an operation of a compressor capable of stably operating a compressor by varying capacitance of resonating capacitors electrically connected to a motor of the compressor when a value of inductance of a motor coil is varied according to an operation load of the compressor, in accordance with a preferred embodiment of the present invention will now be described with reference to FIGS. 5 and 6.

Herein, the present invention includes the same elements of the voltage detector 14, the current detector 12, the microcomputer 15, the power supply unit 11 as in the conventional art, descriptions of which are omitted.

FIG. 3 is a block diagram showing an apparatus for controlling an operation of a compressor in accordance with the present invention.

As shown in FIG. 3, the apparatus for controlling an operation of a compressor includes: a controller (not shown) for generating a control signal for selecting an operation mode of the compressor according to an operation load of the compressor; a first relay 17 electrically connected to a motor 18 consisting of a main coil 19 and a sub-coil 20 and selecting only the main coil 19 or both the main coil 19 and the sub-coil 20 according to the control signal for selecting the operation mode of the compressor; first and second capacitors 16 and 21 connected in parallel to the first relay 17; and a second relay 20 connected to the first capacitor 16 and applying power to the first capacitor or cutting off power applied to the first capacitor 16 based on the control signal for selecting the operation mode of the compressor. Herein, the microcomputer 15 of FIG. 1 can perform the function of the controller.

The controller changes an operation mode of the compressor to a power mode or a safe mode as a voltage inputted to the compressor is changed or an operation load of the compressor is changed. For example, when a voltage inputted to the compressor is increased or when an operation load of the compressor is greater than a pre-set reference load, the controller outputs a control signal for changing the operation mode of the compressor to the power mode to the first and second relays 17 and 21. In addition, if the voltage inputted to the compressor is reduced or if the operation load of the compressor is smaller than the pre-set reference load, the controller outputs a control signal for changing the operation mode of the compressor to the safe mode to the first and second relays 17 and 21. The power mode is a mode for operating the motor 18 installed in the compressor only through the main coil 19 and the safe mode is a mode for operating the motor 18 through both the main coil 19 and the sub-coil 20.

The number of times of winding of the main coil 19 and the number of times of winding of the sub-coil 20 can be constructed to be the same or different. Capacitance of the first and second capacitors 16 and 21 can be preferably determined based on a value of the inductance of the motor coil.

The method for controlling an operation of the compressor in accordance with the present invention will now be described with reference to FIG. 4.

FIG. 4 is a flow chart of a method for controlling an operation of a compressor in accordance with the present invention.

First, the controller operates the compressor according to an operation load of the compressor. For example, if the compressor is installed in an air-conditioner, the compressor is operated based on a desired temperature previously set by a user and a room temperature (step S11). In this case, the controller changes the operation of the compressor to the power mode or to the safe mode base don the pre-set desired temperature and the room temperature. Namely, if a voltage inputted to the compressor is increased or an operation load of the compressor is greater than a pre-set reference load, preferably, the controller changes the operation mode of the compressor to the power mode.

Thereafter, when the operation mode of the compressor is to be changed to the power mode according to the operation load of the compressor, if the operation load of the compressor is greater than the reference load, the controller generates a first control signal for changing the operation mode of ht compressor to the power mode and outputs the first control signal to the first and second relays 17 and 22 (step S12). In this case, various switching devices can be used instead of the relays.

The operation of the apparatus for controlling an operation of the compressor when the operation mode is changed to the power mode will now be described with reference to FIG. 5.

FIG. 5 is a block diagram showing an operation of the apparatus of controlling an operation of the compressor when an operation mode of the compressor is changed to a power mode in accordance with the present invention.

First, the first relay 17 selects only the main coil 19 according to the first control signal outputted from the controller. At this time, power flows through only the main coil 19, and in this case, since power flows only at the main coil 19, a back electromotive force constant of the motor is reduced (step S13).

The second relay 22 applies power to the first capacitor 16 according to the first control signal of the controller so that the power can be applied to the main coil 19 through the first and second capacitors 16 and 21. In other words, when only the main coil 19 is selected, the controller connects the first and second capacitors 16 and 21 in parallel so as to increase the capacitance and perform an LC resonation operation.

Meanwhile, when the operation mode of the compressor is to be changed to the safe mode according to the operation load of the compressor, if the operation load of the compressor is smaller than the reference load, the controller generates a second control signal for changing the operation mode of the compressor to the safe mode and outputs the second control signal to the first and second relays 17 and 22. The operation of the apparatus for controlling an operation of compressor when the operation mode of the compressor is changed to the safe mode will be described with reference to FIG. 6 as follows.

The first relay 17 selects the main coil 19 and the sub-coil 20 according to the second control signal outputted from the controller. At this time, power flows through the main coil 19 and the sub-coil 20, and since power flows at the main coil 19 and the sub-coil 20, the back electromotive force constant of the motor is increased (step S15).

The second relay 22 opens the first capacitor 16 according to the second control signal of the controller to cut off power applied to the first capacitor 16, so that power can be applied to the main coil 19 and the sub-coil 20 through only the second capacitor 21 (step S16). Namely, when the main coil 19 and the sub-coil 20 are selected, the controller cuts off power applied to the first capacitor 16 in order to reduce capacitance and perform an LC resonation operation.

Accordingly, when the value of the inductance of the motor coil is changed according to the operation load of the compressor, the resonating capacitors connected to the motor varies the capacitance values of the resonating capacitors are varied, thereby stably driving the compressor.

As so far described, the apparatus for controlling an operation of the compressor in accordance with the present invention has such an advantage that when the inductance value of the motor coil installed in the compressor is changed, the capacitance values of the capacitors connected to the motor are varied, so that the compressor can be stably driven.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims. 

1. An apparatus for controlling an operation of a compressor comprising: a controller for generating a control signal for selecting an operation mode of a compressor according to an operation load of the compressor; a first switching unit connected to a motor of the compressor having a main coil and a sub-coil, and selecting the main coil or both the main coil and the sub-coil according to the control signal; first and second capacitors electrically connected to the first switching unit; and a second switching unit connected to the first capacitor and selectively connecting the first capacitor in parallel to the second capacitor according to the control signal.
 2. The apparatus of claim 1, wherein if the operation load of the compressor is greater than a reference load, the controller generates a first control signal for selecting the main coil.
 3. The apparatus of claim 2, wherein if the operation load of the compressor is greater than a reference load, the controller generates a first control signal for selecting the main coil.
 4. The apparatus of claim 3, wherein the second switching unit connects the first capacitor to the second capacitor in parallel when the main coil is selected by the first switching unit.
 5. The apparatus of claim 4, wherein the second switching unit cuts off power applied to the first capacitor when the main coil and the sub-coil are selected by the first switching unit.
 6. The apparatus of claim 1, wherein the first and second capacitors are connected in parallel by the second switching unit when the main coil is selected by the first switching unit.
 7. The apparatus of claim 1, wherein one of the first and second capacitors is opened by the second switching unit when the main coil and the sub-coil are selected by the first switching unit.
 8. An apparatus for controlling an operation of a reciprocating compressor comprising: a voltage detector for detecting a voltage applied to a reciprocating compressor as a stroke of the reciprocating compressor is varied; a current detector for detecting a current applied to the reciprocating compressor as the stroke is varied; a microcomputer for calculating a stroke based on the voltage value detected by the voltage detector and a current value detected by the current detector, comparing the calculated stroke with a stroke reference value, generating a switching control signal according to the comparison result, and generating a mode control signal for selecting an operation mode of the reciprocating compressor according to an operation load of the reciprocating compressor; a power supply unit for supplying a stroke voltage to the reciprocating compressor by on/off controlling AC power applied to the reciprocating compressor with an internal triac; a first switching unit connected to a motor including a main coil and a sub-coil installed in the reciprocating compressor, and selecting only the main coil or both the main coil and the sub-coil according to the mode control signal; first and second capacitors electrically connected to the first switching unit; and a second switching unit connected to the first capacitor and selectively connecting the first capacitor in parallel to the second capacitor according to the mode control signal.
 9. The apparatus of claim 8, wherein when the operation load of the reciprocating compressor is greater than a reference load, the microcomputer generates a first control signal for selecting the main coil.
 10. The apparatus of claim 9, wherein when the operation load of the reciprocating compressor is smaller than the reference load, the microcomputer generates a second control signal for selecting the main coil and the sub-coil.
 11. The apparatus of claim 10, wherein when the main coil is selected by the first switching unit, the second switching unit connects the first capacitor to the second capacitor in parallel.
 12. The apparatus of claim 11, wherein when the main coil and the sub-coil are selected by the first switching unit, the second switching unit cuts off power applied to the first capacitor.
 13. A method for controlling an operation of a compressor comprising: a step in which if an operation load of a compressor is greater than a reference load, power is applied to a main coil of a motor of the compressor, and at the same time, first and second capacitors connected to the motor are connected in parallel; and a step in which if the operation load of the compressor is smaller than the reference load, power is applied to the main coil and the sub-coil of the motor of the compressor, and at the same time, one of the first and second capacitors connected to the motor is opened. 